Blender Python convert units to imperial
If it isn't a duplicate q, the answer can certainly be gleaned from the q marked as dupe Is there a bpy function to convert from blender units to Imperial?

scale /= 0.3048  # BU to feet


which pretty much comes from 1bu = 1 metre

import bpy
import space_view3d_panel_measure as pm
scene = bpy.context.scene
uinfo = pm.getUnitsInfo()    

def bu_to_inches(scene, d):
    scale = scene.unit_settings.scale_length
    # 1bu = 1 / 0.3048 ft
    return 12 * scale * d / 0.3048

def inches_to_bu(scene, d):
    return d / bu_to_inches(scene, 1)

# 1 bu in scene units    
x = pm.convertDistance(1, uinfo)
print(x)
# 1 bu in inches
x = bu_to_inches(scene, 1)
print(x)

# 12.33 bu in scene units
x = pm.convertDistance(12.33, uinfo)
print(x)
# 12.33 bu in inches
x = bu_to_inches(scene, 12.33)
print(x)
# how many inches 12.33 bu is to bu
print(inches_to_bu(scene, x))
# how many bu 1 inch is
print(inches_to_bu(scene, 1))